We request funds for the purchase of a Leica Spectral Confocai-Multiphoton Microscope (Leica SP2 MP) for combined imaging and electrophysiological experimentation. There is no multiphoton microscope at Brandeis, and our single confocal microscope cannot be used for combining imaging and electrophysiology. Such an instrument would greatly facilitate the N.I.H. funded research of the user group. It will also benefit other life science researchers at Brandeis interested in live imaging of biological material. The research of the five investigators in the user group is now well poised to take advantage of combined confocal/multiphoton imaging and electrophysiology. Projects include: mechanisms of synapse formation, synaptic plasticity, neuromodulation, and the regulation of intrinsic excitability. Four of the five investigators have a track record in confocal and quantitative imaging, and a different subset of the four have extensive electrophysiological experience. All five investigators have reached the limit of what can be achieved without an integrated system for combining electrophysiology and live imaging. The Leica SP2 MP instrument would be housed in the Imaging Facility that currently houses our confocal. Because we have had a confocal facility for 10 years, mechanisms of operation and maintenance are already in place. The Imaging facility is managed by microscopist with 20 years of experience. He will commit 50% of his time to running and maintaining the SP2 MP, and will be responsible for training as well. Brandeis University and the Biology Department are committed to maintaining this facility. In addition to the user group, the confocal/multiphoton facility will be available to all life science researchers at Brandeis who have a need for this technology on a time-available basis.